WASHINGTON — House Democrats yesterday unveiled an $894 billion plan to reform the health-insurance industry that is paid for by a stiff tax on millionaires.

House Speaker Nancy Pelosi announced the 1,990-page bill, cobbled together from several versions passed through separate House committees, at a boisterous rally on the steps of the Capitol.

Calling it a “historic moment,” she said lawmakers were “on the cusp of delivering on the promise of making affordable, quality health insurance available to every American.”

A controversial key provision would set up a government-run “public option” for people who don’t get care through their employers.

But in a concession to centrists, the bill, heading to the House floor as early as next week, lets the government negotiate with hospitals and insurers over prices.

Liberal Democrats wanted the public option to use Medicare reimbursements rates, arguing it would save money, and now must decide whether to go along or fight.

Officials said the bill would get 96 percent of Americans covered.

The millionaire’s tax, first unveiled in the bill that came out of Harlem Rep. Charles Rangel’s Ways and Means Committee, slaps a surtax of up to 5.4 percent on taxpayers with an adjusted gross income of $1 million for couples, and $500,000 for individuals.

It also puts a tax on medical-device manufacturers, an idea included in Senate health legislation.

Some members of the House Progressive Caucus were fuming yesterday that the plan didn’t include a more “robust” public option, but Democratic leaders said that approach wouldn’t get enough votes to pass.

The bill also includes an “exchange” in which private insurers compete, a requirement that large employers provide coverage or pay a fine, subsidies for small business, and a mandate that individuals get insurance.

Republicans immediately slammed the effort.

“Instead of listening to the American people, Democrats hid behind closed doors and came back with a bill designed to appease the liberal special interests,” said House Minority Leader John Boehner, of Ohio.